Welding is one of the most fundamental processes in the manufacturing industry and is widely used in many applications, such as trains, aircrafts, ships, power plants, chemical processing plants and many others. The quality control of welding joints has direct impacts on the safety of the structure and is an important part of structural quality management. When an equipment is in operation, the endurance of the welding joint is far lower than that of the base metal, and the welded structure may suffer from fatigue failure due to impacts such as dynamic loads. The formation and expansion of fatigue failure can be difficult to detect, and fatigue fracture typically occurs in a short time, causing great economic losses and catastrophic consequences.
Methods for inspection of welding joints include radiographic inspection, ultrasonic inspection, magnetic flaw inspection, and penetration inspection. Currently, these inspection methods of welding joints are performed manually. Many welding joints, such as those on train frames, are located in hard-to-reach areas and offline inspections often involves the cease of the operation and disassembly of surrounding structures. In other cases, the welding joints, such as those on offshore wind turbines, are located in remote areas, where remote inspections are desired. Therefore, it is desirable to have an automatic monitoring method of welding joints with in-situ sensors.